Pyoderma fistulans sinifica (fox den disease): a distinctive soft-tissue infection

Pyoderma fistulans sinifica (PFS, also referred to as fox den disease because its multiple fistulae and sinuses resemble the structure of a fox den) is a distinct chronic infectious disease in which epithelialized tracts form within the subdermal fatty tissue. PFS, which has not been previously described in the English-language literature, must be differentiated from hidradenitis suppurativa, pilonidal sinus, and perianal fistula. The fistulous tracts of PFS are always lined by stratified squamous-cell epithelium but, unlike those of hidradenitis, reach deep into the subcutaneous fat, run epifascially for long distances, and have no relation to skin appendices. We report on 10 men (mean age +/- SD, 36 +/- 5 years) with PFS (mean duration +/- SD, 11 +/- 7 years). Bacterial cultures of affected tissue from these patients yielded a total of 14 facultative and 31 obligate anaerobic species. Treatment consisted of wide en-bloc excision down to the fascia, including all fistulae. Antibiotic therapy temporarily reduced purulent discharge but did not eradicate the infection. Two patients who underwent fistulotomy without wide en-bloc excision developed recurrences.